Pressure responsive controller device



A. W. MESTON Aug. 10, 194s.-

' PRESSURE 'RESYONSIVE CONTROLLER D EVIOE Original Filed flan-.11 6. 946

VQ MES TON mvm 141. EXANDER VIIIIIIIIIIIIIIIIII/II/ 'oR EY Patented Aug. 10, 1948 v PRESSURE RESPCNSIVE CONTROLLER DEVICE Alexander W. Meston, Yonkers, N. Y., assignor to The Sperry Corporation, a corporation of Delaware Continuation of application Serial No. 652,477,.

March c, 1946. This I Serial No. 753,677

16 Claims. (01. 177-380) This invention relates to a sensitive linkage sysapplication June 10, 1947,

tern for generating a signal output proportional to minute movements of a sensitive controller, such as a barometer, and yet capable of operating over a comparatively wide range of variations in atmospheric pressure such as occur in airplanes.

This application is a continuation of my abandoned prior application Serial No. 652,477 filed- March 6, 1946, in the United States Patent Oflice. According to my invention, I place between the sensitive pick-01f and the device responsive to changes of pressure, such as the bellows of an aneroid barometer, a novel form of multiplying linkage having detachable jaws or clutch means for detachably connecting the barometer and the pick-off under different conditions of expansion. By this means, minute movements within 9. limited range of the barometer may be multiplied and a signal'output proportional to such movement produced with a simple, 'small signal generator. Obviously, my invention is not limited for use with a sensitive barometer or altimeter as it may also be used with an air speed meter, to give in either case an output of such .form that it may be used to actuate a servomotor or similar source of power for use in an automatic pilot for aircraft or in an automatic throttle control.

As shown herein, specifically, my invention is used as a barometric controller for maintaining any desired flight altitude in conjunction with an automatic pilot.

Heretofore barometric control means, have ineluded elements such as bearings and pivoted linkages that, in the normal course of operation, have introduced substantial errors into the system. Such losses may arise from the occurrence of socalled dead spots" on the hearings or from lost motion or other inaccuracies in the'mechanical linkages. Sinceit is necessary to rely on the accurate measurement of extremely small movements of the sensitive element of the pressure responsive devices, it is of utmost importance that vision of automatic zeroing or centering means for establishing the proper reference point about which altitude control is to be established.

Another object of this invention is to provide means for eliminating a jolt" or error signal from the subject instrument when it is put into and out of operation.

Another object of the invention is to provide means for disconnecting the barometric device or expansible bellows from a pick-off device so that in addition to facilitating theproper referencing or zeroing of the subject instrument, the cumulative forces of the bellows exerted on the parts connected thereto is avoided while the instrument-equipped craft travels from the ground or initial datum to the, elevation at which altitude control is to take place.

A still further object of this invention is to provide means for automatically damping undesired output signals that may be created in the pick-oil device as a result of spurious craft motion. 1

The invention also relates to the novel features or principles of the instrumentalities described herein, whether or not such are used for the stated objects, or in the stated fields or combinations.

In the drawings, v

Fig. 1 is a perspective view of an embodiment of the invention. 1

Fig. 2 is a detail transverse section, view on line 2-2 of Fig. 1, showing the construction of the cone centering elements.

Fig. 3 is a detail longitudinal section view on line 3-3 of Fig. 1, showing theinterior construcof the damping device.

Fig. 4is a;detail plan view of the mounting and adjusting means for the rear spring strip mounting for the pick-off armature; and i Fig. 5 is a schematic view of another embodiment of the invention incorporating a pressureresponsive device that is responsive to both static and dynamic pressure.-

Generally speaking, this invention has created means that may be used in conjunction with an automatic pilot, whereby slight changes in atmospheric pressure, such as result from small changes in altitude, are .translated into signals or impulses such as voltage changes. These output voltages or signals are applied in the appropriate sense to the pitch' circuit" of the automatic pilot. such that when, for example, the aircraft drifts below the desired altitude, the elevators are caused to be deflected to cause the aircraft to climb back to the predetermined altitude. The

metric device in response to a dynamic or static pressure taking device such as a Pitot tube. The resultant device in the first instance is commonly known as a barometric controller and is used in an automatic pilot system such as shown in Fig. 1

of Patent No. 2,358,803 at Hanson et al. In the second or latter instance, the barometric device or expansible container may be characterized somewhat as drawn in application Serial No. 546,868

and specifically as shown in Fig. 5 of the instant application, which incorporatesa variation of the primary motivation mechanism 10 in the selected embodiment of the present invention. The pickoif need not be electrical, as it could be a pneumatic pick-off as in the Haglund application body of member i6 respectively, and these elements are anchored to member by anchoring means' and I similar to blocks 24 and 24'. The base of the member I6 is in turn pivoted for movement about a horizontal axis at right angles to shaft l9 by' similar spring strips I 1 and I1 and anchoring blocks l8 and I8, respectively, the primed block means being hidden on the right by the bellows of the device Ill. The blocks l8 and I8 are fastened by common screws or rivets to a fixed L-shaped elongated block l5 which is disposed alsoat right angles to rod 9 and shaft 19. the uninterrupted vertical face '5' of the block l5 being normally in the same plane as the sides of members I 6' and 20 facing device Ill. The structure thus far described will permit the movement of the rod element 9 to be substantially aligned with the longitudinal axis of the pressureresponsive device l0 because any tendency of the bellows in device in to have unequally distributed tension qualities around its annulus forauction will be compensated by the refusal of the Serial No. 602,834. Also the Pick-ofi, when of the electrical type, may use either the principles of magnetic induction or capacitive reactance. It is emphasized that while the structure of Fig. 1 is described in connection with an automatic pilot system for aircraft, the present disclosure is not to be limited thereto, since the inventive concept of employing a frictionless drive in the ordinary sense between a, pressure-responsive device and a signal-generating device, known as a pick-01f device, may be practiced in mechanism employed in subsurface craft or missiles. In this case, control of the pressure-responsive device would be typified by a particular diaphragm well known in the submarine art, and since the connection between the same and any depth-controlling mechanism is furthermore delineated in many patents related to liquid submersible craft or devices, itis deemed unnecessary to specifically point out, how such further utility of the present invention is accomplished. Since the instant invention lies primarily in the use of spring mounting means for all moving parts directly aifecting the response of the controller in producing asubstantially linear output, it can be appreciated that no specific control system for movable objects in any specific medium should limit the breadth of this concept.

Referringfirst to Fig. 1, in order to simplify the disclosure of the same, the extremes are described first and the connective elements later along with their respective function with a, pressure-responsive device. Thus, a standard temperature com pensated barometric device Ill may be supported from its standard shafts l4 and I9 by a bracket 1 2 fastened to any convenient base H by screws i3 and a spring-mounted yoke arrangement it, respectively. Shaft i9, having a centralized longitudinal bore I 9 at its outer end for the reception of a slightly flexible rod element 9, is directly connected to a T-shaped member 20 having a protruding portion 2! at the bottom thereof to receive a centralized screw 22 threaded also into a transverse hole mating with the bore l9" and rod 9 therein. Member 20 has two vertically =disposed flexible strips 23 and 23' each depending downwardly from two aligned extremities thereof by block anchoring means 2 and 265m tothe opposite end of each of these strips there is connected the spaced top portions of an intermediate U-shaped member l6 by similar anchoring means 24 and 24'; On the inner top portion of each side of the member W are two spaced inwardly flared elements I and 8' at right angles to the described strip springs to be deformed to any considerable degree about their vertical axes. Also, to further overcome the possibility that the upper and lower half-sections of the aneroid diaphragms may not respond alike to pressure changes either within or without the aneroid bellows l0 when it 'is subjected to acceleration forces, a bracket structure-28 integral with a normally horizontally disposed plate 30 flared outwardly from the U-shaped member IS, the bracket depending below the same, is pivotally supported about a hori-- zontal axis by strip springs 32 anchored to the lower part of U-member l6 and the top part of base l5 by anchors 3i and 3|, respectively, the strip springs and anchors being similar to those already described. An adjustable nut or weight 26 is hungfrom the underside of bracket 28 on a stud 21. By turning adjusting nut 26 one way or the other, the weight of the left end of the barometric device lfl can be counterbalanced to care for the mentioned acceleration forces.

The purpose of the above assembly is to act as the source of motivation, a motion input means, or as a first pressure-responsive means for causing signals to be generated ina pick-off device which may be either of the air type found in many of the automatic pilot systems as in Haglund application Serial No. 602,834 or an electric pick-off 62. Pick-01f device 62 is substantially conventional in that it is composed of an E-type transformer whose output varies in accordance with the changing positions of an armature 6| mounted on pick-oifcarrying means including a main lever 40.. The distinguishing features of device 62 will'be evident from the description of the same hereinafter.

The major portions of the novel apparatus are supported by a U-shaped, light-weight rigid body structure 36 having a bottom portion 36' which is fastened to a base structure II and is disposed able movement within a grooove 29 on the long left vertical face ofsecti on 3G" through a dual 5 threaded set screw 28". the coarse thread going into a threaded end of bar II, the fine thread going into a threaded hole within an ear 2! integral with the part of section II" facing the device 10. Exterior set screws 2O", 20' on top of element 36" directly over the groove 28 provide means for locking and unlocking the slidablebar Ill. Other means of adjustment would serve equally well. Such means of mounting the E- transformer M' of the pick-off M make it possible to adjust the pick-off for zero output under conditions to be explained later.

Between the pick-off device 82 and the pressure-responsive device it there are found a plurality of major parts such as pick-off element carrying means including a main lever 40 containing as a part of itself the spring mounting amazes the lever to be acted upon by an absolute centering device described hereinafter. Therefore, the lever ll including its spring mounting is characterized as a self-centering lever.

A clutch device 50 is formed of two paired substantially T-shaped elements 5!, 5|.- one being placed on one side of the lever 40 at the left partially covering the cut-out portion of the same, and the other being placed on the opposite side of this lever, the elements 5|, 5| being held together by a rivet 54. Elements 52. 52' form the base and gripping or jaw surfaces, respectively, of the T-shaped clutch 50. The clutch B is suspended from the upper part of the lever dd byhaving two outwardly flared portions W and B to which is attached a set of strip springs W The main lever to is aflat rigid vertical platelike member having an irregular cut-out portion disposed to the left of the pivot means on the bottom side of the member and of sumcient dimensions to accommodate a clutch structure presently described. The left section of the lever M also protrudes with an arm to' downwardly and inwardly terminating in a bent portion oi disposed for a -leng th of its extremity at right angles to lever on and pointing toward device it. A block and strip spring arrangement M, similar to the springs 23 and blocks 2% for mounting the same, connects the inward flat side of portion or ear M with a left outside face at of the element 38'. A portion M" below ear tiaccommodates another block and spring arrangement 5 at right angles to the above spring arrangement 66 and is fastened to a front face W of element 382' This construction forms a lower pivot having a vertical axis at the intersection of the strip springs. A similar vertically aligned pivot is formed at the upper part of lever to by flaring out another car M aligned with ear ti to which is' attached spring strip at anchored to the U-side element 36'', and by anchoring at right angles to spring Mi another spring at attached to the top of lever to to element 86". Thus, it is seen that a frictionless pivoting axis or hearing Y-Y is produced for lever MI.

Attached to. the topright side of lever W are found two spacedsets of springs ll, it anchored in the manner already described for the previous spring strips. {To the other ends of these springs ill, to are also fixed an armature base 60. An ear M is formed fromthe lever to between these springs to carry another strip spring to at right angles to the above springs 41 and d8. Attached to the rear end of the armature base 60 carrying armature BI is a rear hinge spring strip", by means similar to block 25, the other end of flexible hinge Ill being" adjustably mounted to the after. hinges I2 is motivated through a lever 16 by either and 5B anchored to brackets 53 and Mwhich are anchored to the lever 40. A coil spring 51 is anchored to the lower. part of ,the clutch 50 and fastened to bottom part at of lever 40, whereby the contacting elements 52 and 52' are moved its the direction of a mating jaw 58 on the lever A clutch release bar H is mounted on two parallel vertical hinge spring "supports 12 formed into a bracket-like base which is anchored by conventional means to the jog element 31' in the base of the structure 86 to provide parallel movement of release bar Ii between a lower inwardly protruding portion E3 of clutch 50 and an armature centering device 85 to be described herein- Release bar II mounted on the spring a spring it or a solenoid mechanism to which is "attached link ll. Lever arm i6 is pivoted about ,apivot 18' in a vertical pillar support i8 mounted rigidly on the base ll. A'pln 19 on the left top of'the release her ll rides in a slot on one end of lever arm 16, the opposite end of said lever arm i6 being pivotally connected by common means TI to the link 'l'i, whose inner end is likewise pivoted to a plunger 80' of the solenoid I5 mounted rigid to the base i i by bracket 15'. Midway between the pivot 18' and the pivot H is fastened the coil spring it, the opposite end being connected to rigid members and 3B fastened to the element 31 of the rigid upright support to. A conventional energizable circuit 82, having a switch 83 therein, is connected to the input wires 50 of solenoid ,iii;

In the present showing of the apparatus of this invention, the switch 83 is opened and hence solenoid i5 is deenergized and spring M is permitted to" move the lever arm 16 counter-clockwise, thereby forcing release lever H to the left against the protruding portion 13 of the clutch .50. Since spring fit is made to have stronger tensioning.

than clutch spring 51, it is seen that the jaws 52, 52' are moved away from the mating jaw 58 against the action of spring 51, thereby permitting a slightly flexible rod 8 which is connected to the pressure-responsive device ID to be free of the clutch. Thus, it is seen that declutching means are provided for the clutch means. When the apparatus is in this condition, additional mechanism should respond to place the armature Si in a position relative to the Iii-transformer 62' such that no output will be derived from the same.

Automatic armature centering device 65 is incorporated into the apparatus for this purpose. The rigid element 38, mentioned above very briefly in connection with the spring 14, is formed as ment 30 is attached a rigid member 85 which, in turn, has anchored thereon a strip spring 66 fastened by block means described heretofore. On the other end of spring 66 is mounted a rigid member 86 carrying at its extreme end a coneshaped structure 81 having a pilot 88 at the top of the cone which is adapted to ride within a centering slot 89 found on a bracket-like structure 90 formed at the lower right hand corner of lever .40, the plane of the slot being at right angles to the main body portion of the lever 40. Also, the rigid element 38 is 50 disposed that the spring 66 is at right angles to lever 40 and, therefore, the action of spring 66 is such as to force the cone 81 partially but snugly into the slot 89, which action will move the lever 40 about the axis Y-Y in one direction or theother depending upon the previous position of the armature before the solenoid I5 was deenergized. Hence, assuming that the armature GI and E-transformer 62' of the pi'ck-oif device 62 have been previously positionally adjusted, it can be seen that the armature centering device 65 will always bring back the armature GI to a position which will produce zero output from the pick-oil 62.

Initial adjustment of the pick-off 82 is obtained with switch 03 open when the craft mounting the novel instrument is at ground level by loosening set screws 26 and 28' holding the E-transformer base 25 in place and then turning thumb-screw 25" until zero output from the pick-off 62 is indicated on any conventional meter (not shown) connected in the transformer circuit. In the event that consistent zeroing of the armature BI after each declutching action of the apparatus is unattainable, further adjustment means for the pick-off 621s provided as shown in detail in Fig. 4,

wherein a member 92 with an overhanging ledge 92' forming a flexible throat 93 is mounted at the back of rigid member 36 by a screw 94 to hold the long spring strip I0 which is retained between member 92 and a member 95 having a ledge 95' overhanging the throat 93 by ordinary rivet means. At the far end of this assembly an adjustment screw 96 is threaded through the same to make end contact with the outer back face of structure 36, whereby movement of strip I0 can be produced about the throat 93 as an axis. This adjusting means also effects the movement of armature BI relative to the pole faces 62" of the E-transformer 62'. An adjusting screw 91 in the ledge 95' and through strip I0 provides additional adjustment of the initial position ofthe armature GI and aids in determining the characteristics of the pick-off output as desired. In this case, it is desired to have a linear output. The strip spring arrangement such as elements l1, l0 and 48 in a right-angle relationship overcomes the effects of certain forces of acceleration upon the armature 6i and its base 60.

Returning to the operation of the apparatus,

it is seen that when the solenoid switch 03 is closed'and the solenoid I5 is energized from circuit 82, the plunger 80' connected through link 11 to lever arm It turns the same clockwise about pivot I8 since the power generated by the solenoid acting through the mechanical advantage from pivot I8 to pivot 11' is stronger than spring ll, thereby forcing clutch release bar II away from the clutch 50, releasing the same for movement by spring 51 and moving the right end of the bar If toward the pilot 88 for contact thereto at its end a moment or at a time point slightly after the clutch jaws 52, 52' and 58 grip rod 9. This delayed tontact between bar II. and pilot 88 is accomplished by having an initial clearance between these two elements slightly greater than a one-waytravel of clutch elements 52, 52'. The above relationship can also be adjustably maintalned by the thumb-screw arrangement II on the left end of release bar II. Thus, the pickoil 62 is held to a very small, if any, jolt or error of signal when the clutching means above engages and disengages the rod 9. Said rod is preferably made sufliciently slender so as to be transversely .flexible or resilient to avoid interposing appreciable resistance to the rotation of lever or plate 40 about the axis Y-Y which might otherwise be interposed through the gripping action of the laws 52, 52' and 58 on the rod when the bellows I0 moves. Additional protection is given the apparatus by making the coil spring 51 sufficiently weak so that slippage of rod 9 through the clutch arms 52, 52 and 58 will occur if sudden and undesirable large displacements of the bellows I0 are encountered.

The mechanical advantage of the main lever 40 is made such that for a minimum change in the position of shaft I9 coupling the rod 9 to the pressure-responsive device I0 due to a change of a few feet in the elevation of the craft, the resulting change in the output of pick-off 62 will be sufiiciently high to be utilized in a standard servo motor setup including an electric amplifiegttor an automatic pilot control system for aircr t.

Damping means I00, shown in detail in Fig. 3 and mounted from two points in the novel apparatus, one point being fixed as on the upper back of the rigid element 36 by a bracket IOI, eliminates undesired output impulses or signals from pick-off 52 produced through a variety of causes. Damping device I00 can be considered a two-part device in that its essential elements comprise a highly magnetic piece such as a cylindrical Ainico pole I02 centered and fixed within an iron cylinder I03, in turn fixed to the bracket IN, and a copper cup-shaped element I05 fitted for movement substantially longitudinally within the cylinder I03 and about pole I02, the cup I05 being mounted on a bracket I06 which is fixed to the top part of lever 40 by rivets I06 on its least mechanical lever arm substantially in line with a vertical plane (not shown) within which rod 9 may be associated. In this manner, cup I05 is subjected to a minimum transverse motion. To increase the magnetic coupling between iron cylinder I03 and the Alnico pole I02, a shallow pole face- Illl of a larger diameter than the pole I02 is press-fitted over the exposed end of the same. The above structure dampens the movement of the inherently self-centering lever 40 carrying pick-off element carrying means and other parts directly coupled to the same in a characteristic fashion well known to the electrical art.

Since, as explained'in the general summary of the invention, the concept of employing frictionless apparatus in conjunction with pressure-responsiveand pick-ofi devices is not limited for use in a situation demanding altitude control of aircraft through the application of mere static pressure to the pressure-responsive means, additional control of aircraft is shown in Fig. 5, demonstrating schematically how the structure of Fig. 1 may be altered for use in connection with altitude control, banking control or even speed control of aircraft using dynamic pressure as the additional power-generatingsource for thepickof! device. In this case, the described apparatus of Fig. .1 would be placed in a container airtight except for openings therein permitting entrance of tubing Ill and H2. Tubing IIZ, forming the static pressure air line, leads directly to the interior of anerold device ill from an air accumulator H3 outside the aircraft, while tubing Ill forms the dynamic air line from the accumulator H3 to the immediate interior of the container H0. The signal generator and coupling apparatus labeled I I5 is a block representation of the pick-off device .82 and coupling apparatus interposed between the same and the pressure-responsive device l0, respectively, the control circuit 82 of solenoid 15 being found outside the container llll, and this likewise holds true for output leads I I6 from the pick-oil.

The novelty of this invention from a broad viewpoint resides in the means of obtaining an output of appreciable magnitude 'from small sources of 'power through a mechanical system without the use of friction means connecting an input source to the output and hence the scope of the invention is not to be limited by the present embodiments of the same.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without, departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a device of the character described, the

I combination of motion input means, a rod-like element coupled at one end to said means, a lever coupled to the other end of said element, means for self -centralizing said lever,-a pick-off producing an output and including a movable element connected to said lever and clutch means for coupling and uncoupling said rod-like element and said lever, said lever moving responsive to actuation by said input means to cause the output of said pick-off to change correspondingly.

2. In a device of the character described, the combination of a first pressure-responsive means, a transversely resilient element coupled at one i 10 5. In a device ofthe character described, the combination of a first pressure-responsive means. a pick-on including a movable element, pick-oi! clement carrying means including a lever, clutch .means mounted on said lever, motivating means for said clutch means, and means including a transversely flexible element responsive to said first means interposed between the same and said clutch means, whereby increments of pressure changes on said first means effect substantially linear increments in the output of said pick-oil.

6. In a device of the character described, the combination of a first pressure-responsive means, a pick-off including a movable element, clutch means, pick-off element carrying means including a lever between said pick-off and said clutch means, motivating means for said clutch means, and means including a flexible element responsive to said first means interposed between the same and said clutch means, and centralizing means coupled to said pick-off element carrying means whereby varying pressure changes on said first means produce substantial changes in the output of said pick-ofi, said clutch means including the motivating means facilitating a zero si nal position for said movable element at any altitude below a predetermined level.

'7. In a device of the character described, the

combination of a first pressure-responsive means,

an electric pick-oil, armature carrying means ineluding a lever, frictionless mounting means for vsaid lever, and means including a transversely end to said first means, a lever coupled to the other end of said element, means for centralizing said lever, and a pick-ofiincluding a movable element connected to said lever and producing an output, said lever moving responsive to actuation by said first means to cause the output of said pick-oil to change correspondingly.

3. In a device of the character described, the combination of a first pressure-responsive means, a rod-like element coupled at one end to said first means, a self-centering lever coupled to the other end of said element, clutch means integral with said lever for coupling and uncoupling the same to the other end of said element, and a pickoff including amovable element connected to said lever whereby varying pressure changes on said first means are translated to said pick-off which produces a substantially linear output.

4. In a device of the character described, the combination of a first pressure-responsive means, a pick-off including a movable element, a pick-ofi element carrying means including a lever, spring mounting self -centering means for said lever, and means including a transversely flexible element responsive to said first means interposed between the same and said lever whereby varying pressure changes on said first means are transferred to said pick-oil.

yielding elongated element responsiv to said first means interposed between the same and said ar-' mature carrying means whereby varying pressure changes on said first means introduce substantial positional changes of said movable armature to effectcorrespondingoutput changes of said pick-oif.

8. In a device of the character described, the combination of a first means, an electric pick-off device including a movable armature, clutch means, pick-off armature carrying means including a lever between said pick-ofi and said clutch means, said clutch means including pivoting means on said lever, motivating means for said clutch means, and means including a rod-like element responsive to said first means interposed between the same and said clutch means whereby varying pressure changes on said first means pro duce substantial changes in the output of said pick-off when said rod-like element is engaged by said clutch.

9. In a device of the character described, the.

combination of a first pressure-responsive means, an electric pick-off device including a movable armature, clutch means, pivoting means for said clutch means, pick-off armature carrying means including a lever between said pick-off device and.

said clutch means, activating means for said clutch means, means including a transversely flexible elongated element responsive to said first means interposed between the same and said clutch means, and means coupled to said armature carrying means for damping the movement of said movable element whereby varying pres- .sure changes 'on said pressure-responsive device produce substantial changes in the output of said pick-off device without distracting energy inputs to said device being superposed on said pick-oil changes.

10. In a device of the character described, the combination of a first pressure-responsive means, a pick-off including a movable element, paired clutch elements, pivoting means for said clutch elements, a pick-oi! carrying means including a lever between said pick-oil and said clutch elements, activating means for said clutch elements. means including an elongated, transversely yieldin: element responsive to said first means interposed between the same and said clutch elements, and means for positively centering said movable element upon disconnection of said first means from said element carrying means, whereby varying pressure changes on said iirst means produce substantially linear changes in the output of said pick-oi! from a zero reference output point of the same corresponding to any pressure datum below a predetermined maximum.

11. In a device of the character described, the combination of a first pressure-responsive means, a pick-oil, including a movable element, clutch means, pivoting mean for said clutch means, pick-oi! carrying means including a lever between said plck-ofl device and said clutch means, activoting means for said clutch means. means responsive to said first means interposed between the same and said clutch means, means coupled to said element carrying means for damping the movement of said movable element, and means for zeroizing said pick-on upon disconnection of said first means from said element carrying means, whereby pressure changes on said first means institute amplified changes in the output of said pick-ofl.

12. In a device of the character described, the combination of a first motion input means, an electric pick-oi! including a movable armature, clutch means, pivoting means for said clutch means, pick-oil armature carrying means including a spring mounted lever between said pickof! and said clutch means, activating means for said clutch means, means including a transversely flexible element responsive to said first means interposed between the same and said clutch means, and means for zeroizing said pick-off upon disconnection of said first means from said armature carrying means, said lever moving responsive to actuation by said input mean to cause the output of said pick-oi! to change linear- 1y upon engagement of said flexible element by said clutch means. i

13. In a device of the character described, the combination of a first pressure-responsive means, an electric pick-oil including a movable armature, clutch means including Jaws, pick-of! armature carrying means including a mechanical amplifying mechanism between said Pick-oil and said clutch means, said jaws being part of said mechanism, activating and deactivating means for said clutch means, means including a rodlike element responsive to said first means interposed between the same and said clutch means, means coupled to said'armature carrying means for damping the movement of said movable armature, and mean for positively centering said movable armature upon disconnection of said first means from said armature carrying means.

14. In a device used in an automatic height control system for aircraft, the combination comprising a barometric device, a pick-oi! including a movable element, a main lever, spring mounting means for said lever, spring means interposed between said movable element and said main lever,rclutch means. pivoting means for said clutch means mounted on said main lever, means interposed between said clutch means and said barometric device, and activating means coupled to said clutch means whereby said barometric device may be used for causing impulses to be generated about a zero reference impulse point corresponding to any altitude below a predetermined maximum elevation.

15. In a device used in an automatic height control system for aircraft, the combination comprising a barometric :device, a pick-oi! including a movable element, a main lever, spring mounting means for said lever, spring means interposed between said movable element and said main lever, clutch means, pivoting means for said clutch means mounted on said main lever, means interposed between said clutch means and said barometric device, and activating means for said clutch means, and a two part dampingmeans. one part being mounted at a fixed point, the other part being mounted on the main leverwhereby said barometric device may be used for causing a signal to be generated about a null reference point corresponding to any altitude below a predetermined maximum elevation.

.l6. In a device of the character described, the combination comprising a' first pressure-responsive device, a pick-oi! including a movable element, 9. main lever, spring mounting means for said lever, means interposed between said first device and said main lever, clutch means, pivoting means for said clutch means mounted on said main lever, declutching means intermittently coupled to said clutch means, a two-part damplng means, one part being mounted at a fixed point, the other part being mounted on the main lever, and centering means including a springmounted centering arm whereby said first device may be used for causing signals to be generated about a zero reference point at any altitude below a predetermined maximum elevation.

ALEXANDER. W. MESTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,407,657 Esval Sept. 17, 1946 2,227,055 Bishofl Dec. 31, 1940 

